Investigation on impact performance and dimensional stability of polypropylene composites in cryogenic environment

Polymer Waste-Based Highly Efficient Maleated Interfacial Modifier in iPP/SCF Composites—Some Notes on the Role of Processing in Their Thermal and Dynamic Mechanical Properties

This work has a two-fold objective. First, it attempts to present the excellent efficiency of a maleated interfacial agent (obtained by the authors by using atactic polypropylene industrial waste) when used as interfacial additive in polypropylene/short carbon fiber composites (iPP/SCF). Second, in this paper, we pay attention to the role played by processing in the final properties of the composite. This work has been performed by considering the emerging crystalline morphologies generated by the different shear forces that the molten material suffers depending on the molding method employed. The interfacial agent analyzed here consists of an atactic polypropylene containing succinic anhydride grafts obtained through a chemical modification process performed in solution. It incorporates different types of succinic grafts, such as succinic bridges between aPP chains and backbone and terminal grafts (aPP-SASA) in its structure, and contains 5.6% (5.6 × 10−4 g/mol) of grafted polar groups in total. The adhesion of the polyamide SCF sizing and the succinic units is followed by Field Emission Scanning Electronic Microscopy (FESEM) and Synchrotron Infrared Microscopy (SIRM). However, the main objective of this work is the study of the thermal and the dynamic mechanical behavior of the materials of a series of both compression- and injection-molded samples to ascertain the enhanced interfacial interactions in the material and further comparison between the results obtained by both processing operations. Therefore, we detect improvements of 200% in stiffness and 400% in the viscous response of the same SCF content composites caused by aPP-SASA, depending on the processing method used.

The preparation and evaluation mechanism of mesoporous spherical silica/porous carbon-filled polypropylene composites obtained from coal gasification fine slag

Coal gasification fine slag is a by-product of the entrained-flow gasifier, which has caused some environmental pollution. Through acid dissolution and calcination at different temperatures, mesoporous spherical silica/porous carbon composite filler was prepared using coal gasification fine slag. The particle size and specific surface area of the composite filler decreased with the decrease of unburned carbon content. The analysis of X-ray photoelectron spectroscopy (XPS) indicated the decrease of oxygen-containing functional groups and the increase of C-C groups with the decrease of the content of carbon. The effects of mesoporous spherical silica/porous carbon with different carbon content on the comprehensive properties of filled polypropylene (PP) were studied. The tensile strength and interface interaction increased at first and then decreased with the decrease of carbon content, due to the synergistic effect of mesoporous spherical silica and rough amorphous carbon. The scanning electron microscope showed that the composite filler with the carbon content of 14.47 wt.% at the calcination temperature of 450 °C had the best compatibility with the matrix. Thermodynamic analysis of the PP composites indicated that thermal insulation properties and thermal stability improved with the incorporation of the composite filler. Differential scanning calorimetry (DSC) testing indicated the highest crystallinity of the matrix corresponding to the best comprehensive performances of the composites. XRD patterns revealed that the cooperation of fillers brought characteristic peaks and did not change the primary crystal structure of PP. Simultaneously, heavy calcium powders (CC) were used as comparative fillers, and the overall properties of the PP composites filled with the composite filler were better compared to those of the CC-filled PP composite. The results illustrated that mesoporous spherical silica/porous carbon particles can completely replace CC used in the PP composites, which can be used in auto bumpers, plastic pipes, display cases, and car air deflectors. The CGFS can be processed into a plastic filler for substituting heavy calcium powder particles, which can solve the environmental pollution caused by the accumulation of solid waste.